Agrobacterium rhizogenes-Mediated Transformation as a Means for Induction of Hairy Roots and Secondary Metabolites in Thymus daenensis

Thymus is a medicinal plant, species of which are used in ethnomedicine. This study is aimed at hairy root induction in Thymus daenensis using Agrobacterium rhizogenes strain ATCC15834, and its strains harboring pRiA4, pRi2659 and AR9534 plasmids to enhance secondary metabolite production in the transgenic plants. Therefore, roots, leaves and stems of seed-derived explants of T. daenensis were transformed by plasmid-borne rolB and rolC genes for induction of hairy roots. Total phenolics and flavonoids in transgenic tissues were measured by Folin-ciocalteu and Aluminum chloride methods, and the chemical compositions of the transformed roots of T. daenensis were identified by GC-MS. Results indicated that A. rhizogenes strain ATCC15834 and A. rhizogenes harboring pRiA4 plasmid were capable of hairy roots induction. The highest percentages of hairy root inductions were observed in leaf explants. The PCR analyses confirmed the transfer of rolB and rolC genes to T.daenensis. The content of the major chemical constituents of the transgenic roots of T. daenensis, including thymol and carvacrol, were increased. The highest total phenolics (209.28 mg GA/g) and flavonoids (4.29 mg Q/g) were obtained from the roots transformed by A. rhizogenes strain ATCC15834. In conclusion, A. rhizogenes-mediated transformation is being introduced as a convenient method for hairy root induction in T.daenensis, and for enhancing its secondary metabolite production.